hdoj3068--最长回文(manacher模板)

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 110055;

char s1[maxn], s2[2*maxn];
int p[2*maxn];

void init() {
s2[0] = '@', s2[1] = '#';
for(int i = 0, l = 2; s1[i]; i++, l += 2) {
s2[l] = s1[i];
s2[l+1] = '#';
}
}

int manacher() {
int ans = 0, mx = 0, id;
for(int i = 1; s2[i]; i++) {
if(mx > i) p[i] = min(p[2*id-i], mx-i);
else  p[i] = 1;
while(s2[i+p[i]] == s2[i-p[i]]) p[i]++;
if(p[i]+i > mx) {
mx = p[i]+i;
id = i;
}
ans = max(ans, p[i]);
}
return ans-1;
}

int main() {
int T = 0;
while(~scanf("%s", s1)) {
init();
printf("%d\n", manacher());
memset(s1, 0, sizeof(s1));
memset(s2, 0, sizeof(s2));
}
return 0;
}